Guessing ~15-20 minutes. It was pretty quick. Hardest part was trying to remove the console cover without getting ugly pry marks on the hinge frame. Next hardest part was depressing the proprietary GM mini usb connector lock tab. Ended up using a small screwdriver to press the stupid tab down.

Time's about right- 20 min or less 1st screw out to last screw back in...

Success.
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.
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Still pisses me off that the first thing to come up on my iPhone (3GS) is:
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"This Accessory is Not Optimized for this iPhone...yada, yada, yada..." WTF?
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The iPod/iPhone is probably the most used "accessory" with this car's setup from what I see- God forbid Apple and GM got their shit collectively together...But, hey, if everything now works (ALL the time and not when it wants to) and all I have to do is ignore that message, I'm good with it.